Push-button switch

ABSTRACT

A snap acting switch includes a pair of spring contact arms carried at one end of a drum mounted for slidable movement on a stationary member and movable by an external force to a switchclosed position in which the spring contact arms are in pressure engagement with fixed contacts located exteriorly of the drum. The drum is held in switch-closed position against the spring pressure of the engaged contacts, by means of a plurality of balls located in through radial bores in the drum, and recessed seats in the stationary member receiving said balls. Biasing means, such as a rubber ring, is mounted on the drum and maintains said balls in seated positions in the recessed seats.

United States Patent Bartens, deceased et al. [451 July 11, 1972 [54] PUSH-BUTTON SWITCH [56] References Cited 72 Inventors: Carl Emil Bartens, deceased, late of UNITEDSTATES PATENTS Denma'k; by E 2,386,162 10/1945 Hetherington ..200/77 tens; by Bjoern Bartem, both of Moerke, Denmark heirs Assignee: Kristian Krog Sorensen, Sonderbro, Aalborg, Denmark Filed: March 25, 1971 Appl. No.: 128,096

Primary Examiner-David Smith, Jr. Anomey-Edward F. Levy ABSTRACT A snap acting switch includes a pair of spring contact arms carried at one end of a drum mounted for slidable movement on a stationary member and movable by an external force to a switch-closed position in which the spring contact arms are in an Application Priority pressure engagement with fixed contacts located exteriorly of Nov. 8, 1968 Denmark ..s437 the drum- The drum is held in ewitehelesed Position against the spring pressure of the engaged contacts, by means of a pluus. Cl ..200 17 relity of balls located in through redial bores in the drum. and 1 CL n 110", 15/18 recessed seats in the stationary member receiving said balls. Field at Search ..200/76 77 Biasins means, such as a rubber ring, is mounted on the drum and maintains said balls in seated positions in the recessed seats.

8 Claim, 2 Drawing Figures Z 4 f /f a 7 PUSH-BUTTON SWITCH The present invention relates to a snap acting electrical switch of the type in which one or more pairs of contact arms are mounted on a movable member to be brought in and out of engagement with a respective pair or pairs of fixed contacts in order to electrically correct and disconnect the latter.

In this type of switch it is desirable that the movable contacts arms be springy or be spring loaded so that they engage the fixed contacts with a biasing pressure, thereby assuring firm and efiective engagement and disengagement of the contacts, without sparking. For this purpose, the movable contact arms must be moved to their engaged position by an external force sufficient to press them against the fixed contacts.

In switches of this type where the contacts engage and are maintained under pressure, it is necessary to provide an arresting mechanism capable of holding the contacts in their engaged positions against the spring force which would tend to separate them. There are presently known several different types of switches in which these two functions, namely the establishment of pressure between the closed contacts and the arresting of the switch in its contact-closed position, are accomplished by a single element which includes spring means and some type of tip mechanism.

An object of the present invention is to provide a snap acting switch of the character described which will effectively perform both of the required contact-closing and holding functions with an assembly of a minimum number of parts which are simpler and more economical than those in presently-known switches.

Another object of the invention is the provision of a snap acting switch of the type described which operates with a snap-acting closing operation which effectively eliminates sparking between the contacts.

A further object of the present invention is to provide a snap acting switch of the character described which is exceedingly compact to such extent that its over-all maximum size is determined by the size of its contacts rather than the size of its pressure and arresting components.

In accordance with the invention, there is provided a snap acting switch which comprises a stationary bushing and a drum mounted for sliding movement on said bushing and carrying a pair of movable contact members at one end thereof, said movable contact members being positioned to engage a pair of fixed contact members mounted exteriorly of said drum. The drum is formed with a plurality of radial bores in each of which a ball is movably contained, and the stationary bushing on its surface is provided with a pair of indented ball seats spaced longitudinally thereon and aligned with each of the respective bores. Drive means are also coupled to the drum for moving the latter on said bushing in a first direction to a switch-open position in which the balls are seated in one of the ball seats of said pair, and in which the balls are seated in one of the ball seats of said pair, and in which the movable contact members are pressed against the fixed contacts. The drive means is also adapted to move the drum in the opposite direction to a switch-open position which the balls are seated in the other ball seat and the movable contact members are spaced from the fixed contacts. The switch also included biasing means urging the balls through the radial bores into firm seated positions in the respective ball seats for releasably retaining the drum in either of its two positions.

The drum may also have movable contact members mounted on the opposite end thereof and adapted to engage another set of fixed contacts mounted opposite the other side of the drum.

Additional objects and advantages of the invention will become apparent during the course of the following specification when taken in connection with the accompanying drawings in which:

FIG. 1 is a central vertical section through a snap-acting switch made in accordance with the invention; and

FIG. 2 is a section taken along line 2-2 of FIG. 1.

Referring in detail to the drawings, the pressure changeover switch is shown as having a housing formed of two circular end plates 1 and 1a made of electrically insulating material such as plastic, and a cylindrical housing wall disposed between the end plates and connection the latter to fonn a closed housing. At their centers, the end plates 1 and 1a are also connected and supported by a tubular bushing 3 which extends therebetween and is made of a metal, such as brass.

Surrounding the bushing 3 and slidably mounted thereon is a movable drum 4 having an annular groove 4a extending centrally around its circumference. Four spaced radial through bores 5 are also fonned in the drum 4 in registry with the annular groove 4a. The bores 5 are each of slightly larger diameter than the width of the ridge 4a and are sized to permit passage of respective balls 6 therethrough.

A rubber ring 7, mounted in the annular groove 4a, overlies the balls 6 and biases them inwardly through their respective radial bores 5 and into contact with the bushing 3. The bushing 3 is provided on its outer surface .with a pair of longitudinally-spaced ball seats or pockets. These ball seats 8 and may be in the nature of a pair of spaced annular grooves extending respectively around the circumference ofbushing 3, or they may be in the nature of a pair of indented concavities aligned with each of the radial bores 5 of drum 4. In either event, the seats 8 and 8a are indented and are curved to conform to the size of the balls 6 to provide snug seats therefor. Between each pair of ball seats 8 and 8a is a ridge 9 which is narrow and has a rounded top, the depth of said ridge 9 being less than the diameter of ball 6.

A shaft 10 extends slidably through the tubular bushing 3, said shaft being coupled to the movable drum 4 by a pin 11 which extends through shaft 10 and projects at opposite sides thereof. The projecting ends of pin 11 extend through a pair of respective elongated slots 12 which are located on opposite sides of tubular bushing 3, the pin ends being then fixedly secured to the inner circumference of drum 4. Thus, while the tubular bushing 3 is rigidly mounted in the housing and is immovable relative thereto, when the shaft 10 is slid in either direction within said bushing 3, the sliding motion is imparted to the outer drum 4. Such simultaneous movement of the shaft 10 and drum 4 relative to the fixed bushing 3 is permitted by free movement of the coupling pin 11 through the aligned elongated slots 12. It will be apparent that the lengths of slots 12 determine the extent of sliding movement of axle l0 and its coupled drum 4.

At one end surface of drum 4 is mounted a pair of movable contacts in the form of curved strips or fingers 13 made of a springy metal. The strips 13 are secured to the drum 4 by rivets (not shown) and make electrical contact with each other through drum 4 if the latter is made of conductive material, or through bushing 8 with which the strips have a wiping action. The strips 13 are positioned to engage and make pressing contact with a pair of respective fixed contact members 14 which extend through the end plate 1 and are each secured to a soldering lug 15 exteriorly of the housing. The soldering lugs may be connected in a circuit to serve as switch terminals therefore.

At the opposite end of drum 4 a pair of movable contacts 13', identical to the contacts 13, are similarly mounted. Movable contacts 13' are positioned to engage and press against a pair of respective fixed contacts 14 which pass through end plate 1a and are secured to soldering lugs 15 which may be connected in a different circuit.

In the position of the switch shown in FIG. 1, all four bores are seated in their corresponding seats 8 and are pressed down therein by the elasticity of the rubber ring 7. This locates the drum 4 in a position in which it holds the movable contact strips 13 in firm pressing engagement with the respective fixed contacts 14 so the contacts are closed under spring pressure and good electrical contact is made therebetween. The pair of fixed contacts 14 are thus connected together within the housing. At the other side of the drum 4, the movable contact fingers 13' are spaced from the respective fixed contacts 14 and the switch elements at this side are open. The elastic pressure of ring 7 upon the four balls 6 maintains the balls firmly seated in the seats 8, so that the drum 4 is maintained in this operative position.

When shaft is pulled to the right from its position of FIG. 1, the pin [0 draws drum 4 in the same direction and the balls 6 are forced from the seats 8 against the pressure of rubber ring 7. The balls roll over the rounded top of the ridge 9 and as soon as they have passed the ridge apex, the rubber ring 7 presses them down into the respective seats 8. The drum 4 is now held in its other operative position in which it holds contact strips 13' in firm pressing, spring pressured engagement with the fixed contacts 14', thereby closing the switch elements at the right-hand side. In this second operative position, the movable contact strips 13 are spaced from the fixed contacts 14.

The ball seats 8 and 8a are made sufficiently deep that the balls 6 are held securely therein, under tension of the rubber ring 7, when the switch is in either of its two operative positions despite the tendency of the closed, spring pressured con-- tacts to separate. Thus the drum 4 is maintained in its switch closed positions against sliding movement until external force is applied thereto through shaft 10.

The rubber ring 7, balls 6 and seats 8, 8a all work together as trip mechanism which provides a snap action causing the last portion of the sliding movement to take place at high velocity. This is effected by the biasing force of the rubber ring 7 in urging the balls 6 downwardly into their seats. In addition, the switch parts may be so arranged that the contact pairs open quickly to reduce the possibility of contact arching. For this purpose, the movable contact strips 13 may be so located that they move out of contact with the fixed contacts 14 only after the balls 6 have passed over the apex of ridge 9 and is descending into its seat 8, i.e. during the high velocity end portion of the movement of drum 4. The movable contact strips 13' may be similarly arranged to break contact during the high speed movement of drum 4 in the opposite direction.

While a preferred embodiment of the invention has been shown and described herein, it is obvious that numerous omissions, changes and additions may be made in such embodiment without departing from the spirit and scope of the invention. For example, the number of balls employed may be varied as desired, the arrangement of the contacts may be modified, and in place of the rubber ring, springs or other types of biasing means may be used.

What is claimed is:

l. A snap acting switch comprising a stationary bushing, a drum mounted for sliding movement upon said bushing, a pair of fixed contact members mounted exteriorly of said drum, a pair of movable contact members mounted on one end of said drum and positioned to engage said fixed contact members when said drum is moved toward said fixed contact members, a plurality of radial bores in said drum, a ball movably contained in each of said bores, a pair of longitudinally-spaced ball seats on the surface of said bushing in alignment with each of the respective bores, drive means coupled to said drum for moving the latter longitudinally upon said bushing in one direction to a first position in which said balls are seated in the first ball seat of said pair and the movable contact members are pressed against said fixed contacts, and in the opposite direction to a second position in which said balls are seated in the other seat of said pair and said movable contact members are spaced from said fixed contact members, and biasing means on said drum urging said balls radially inward through the respective bores into firm seated positions in said seats, whereby said drum is releasably maintained in its respective first and second positions, said bushing being a hollow tube having at least one elongated slot therein, said drive means including a shaft slidably mounted in said bushing, and a pin connecting said shaft and said drum through said elongated slot.

2. A snap acting switch according to claim 1 in which one of said pairs of contact members is spring loaded, said drum in said switch-closed position maintaining said pairs of contacts engagfd under spring pressure.

snap-acting swrthch according to claim 1 in which said drum has a circumferential slot registering with each of said bores, said biasing means comprising an elastic ring received in said slot and overlying the balls in said bores.

4. A snap-acting switch according to claim 1 in which a relatively narrow ridge separates the longitudinally spaced seats on said bushing.

5. A snap-acting switch according to claim 4 in which said seats are so located with relation to said contacts that said movable contacts are maintained in engagement with said fixed contacts until the center of said balls have passed over the apex of the ridge between said seats.

6. A snap-acting switch according to claim 1 in which said movable contact members comprise a pair of resilient contact strips mounted on one end portion of said drum.

7. A snap-acting switch according to claim 1 which includes a second pair of fixed contact members mounted exteriorly of said drum, and a second pair of movable contact members mounted on the end of said drum opposite the end carrying said first pair of movable contact members, said second pair of contact members being positioned to engage said second pair of fixed contact members when said drum is brought to its second position and said balls are seated in said other seat of said pair.

8. A snap-acting switch according to claim 7 in which said first and second pairs of movable contact members comprise pairs of resilient contact strips mounted on the respective end portions of said drum. 

1. A snap acting switch comprising a stationary bushing, a drum mounted for sliding movement upon said bushing, a pair of fixed contact members mounted exteriorly of said drum, a pair of movable contact members mounted on one end of said drum and positioned to engage said fixed contact members when said drum is moved toward said fixed contact members, a plurality of radial bores in said drum, a ball movably contained in each of said bores, a pair of longitudinally-spaced ball seats on the surface of said bushing in alignment with each of the respective bores, drive means coupled to said drum for moving the latter longitudinally upon said bushing in one direction to a first position in which said balls are seated in the first ball seat of said pair and the movable contact members are pressed against said fixed contacts, and in the opposite direction to a second position in which said balls are seated in the other seat of said pair and said movable contact members are spaced from said fixed contact members, and biasing means on said drum urging said balls radially inward through the respective bores into firm seated positions in said seats, whereby said drum is releasably maintained in its respective first and second positions, said bushing being a hollow tube having at least one elongated slot therein, said drive means including a shaft slidably mounted in said bushing, and a pin connecting said shaft and said drum through said elongated slot.
 2. A snap acting switch according to claim 1 in which one of said pairs of contact members is spring loaded, said drum in said switch-closed position maintaining said pairs of contacts engaged under spring pressure.
 3. A snap-acting switch according to claim 1 in which said drum has a circumferential slot registering with each of said bores, said biasing means comprising an elastic ring received in said slot and overlying the balls in said bores.
 4. A snap-acting switch according to claim 1 in which a relatively narrow ridge separates the longitudinally spaced seats on said bushing.
 5. A snap-acting switch according to claim 4 in which said seats are so located with relation to said contacts that said movable contacts are maintained in engagement with said fixed contacts until the center of said balls have passed over the apex of the ridge between said seats.
 6. A snap-acting switch according to claim 1 in which said movable contact members comprise a pair of resilient contact strips mounted on one end portion of said drum.
 7. A snap-acting switch according to claim 1 which includes a second pair of fixed contact members mounted exteriorly of said drum, and a second pair of movable contact members mounted on the end of said drum opposite the end carrying said first pair of movable contact members, said second pair of contact members being positioned to engage said second pair of fixed contact members when said drum is brought to its second position and said balls are seated in said other seat of said pair.
 8. A snap-acting switch according to claim 7 in which said first and second pairs of movable contact members comprise pairs of resilient contact strips mounted on the respective end portions of said drum. 